Field of the Invention
The invention relates to a display device, and specifically relates to a head-mounted display.
Description of Related Art
Currently, near eye display (NED) and head-mounted display (HMD) are killer products during next generation. They have great potential for development. The NED is currently applied to augmented reality (AR) and virtual reality (VR). In terms of VR, it is important to create realistic in the virtual world in development. In terms of AR, the developers focus on how to provide the best image quality within a thin and light device.
Furthermore, an image light beam used for display is emitted by a projection device in a basic optical structure of a head mounted display that is used to actualize AR, the image light beam is then reflected by a semi-reflective semi-transmission optical device to enter into the user's eyes. The light beam of the display image and the external ambient light beam all enter into the user's eyes to achieve the display effect of AR. However, in the above-mentioned structure, it is inevitable that the projection device appears in field of view (FOV) of user's eyes, and the above component occupies a certain space. Therefore, the viewing angle of the image displayed by the head mounted display is greatly limited. In order to achieve a wide FOV effect, one conventional solution is to reflect the image light beam multiple times based on a group of optical mirrors or a reflection system, thus, the projection device can dispose outside of the FOV of user's eyes. However, the group of optical mirrors or the reflection system usually increases the volume and the weight of the head mounted display, and a plurality of reflective surfaces of the group of optical mirrors requires extremely high precision in assembling and flatness. Otherwise, another conventional solution is to guide the image light beam from the projection device to the user's eyes based on the light guiding member having mutually bonded multilayer light splitting structure. However, the manufacturing process of the light guiding member includes complicated processes such as coating, bonding, alignment, cutting and polishing, consequently. Thus, it is more difficult to produce the light guiding member. Therefore, it is one of the key points to achieve the wide FOV effect that reduce volume and weight of the head mounted display and simplify the manufacturing process at the same time for the people in the related art.
The information disclosed in this “Description of Related Art” section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the “Description of Related Art” section does not mean that one or more problems to be resolved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.